import React, {PureComponent} from "react"

export default class ZhiFu extends PureComponent {

  render() {
    return (
      <canvas id="zhifu" style={{position: "absolute"}}/>
    )
  }

  componentDidMount() {
    //定义画布宽高和生成点的个数
    let WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 35

    let canvas = document.getElementById('zhifu')
    canvas.width = WIDTH
    canvas.height = HEIGHT
    let context = canvas.getContext('2d')
    context.strokeStyle = 'rgba(255,255,255,0.04)'
    context.strokeWidth = 1
    context.fillStyle = 'rgba(255,255,255,0.08)'
    let circleArr = []

    //线条：开始xy坐标，结束xy坐标，线条透明度
    function Line(x, y, _x, _y, o) {
      this.beginX = x,
        this.beginY = y,
        this.closeX = _x,
        this.closeY = _y,
        this.o = o
    }

    //点：圆心xy坐标，半径，每帧移动xy的距离
    function Circle(x, y, r, moveX, moveY) {
      this.x = x,
        this.y = y,
        this.r = r,
        this.moveX = moveX,
        this.moveY = moveY
    }

    //生成max和min之间的随机数
    function num(max, _min) {
      let min = arguments[1] || 0
      return Math.floor(Math.random() * (max - min + 1) + min)
    }

    // 绘制原点
    function drawCricle(cxt, x, y, r, moveX, moveY) {
      let circle = new Circle(x, y, r, moveX, moveY)
      cxt.beginPath()
      cxt.arc(circle.x, circle.y, circle.r, 0, 2 * Math.PI)
      cxt.closePath()
      cxt.fill()
      return circle
    }

    //绘制线条
    function drawLine(cxt, x, y, _x, _y, o) {
      let line = new Line(x, y, _x, _y, o)
      cxt.beginPath()
      cxt.strokeStyle = 'rgba(255,255,255,' + o + ')'
      cxt.moveTo(line.beginX, line.beginY)
      cxt.lineTo(line.closeX, line.closeY)
      cxt.closePath()
      cxt.stroke()

    }

    //初始化生成原点
    function init() {
      circleArr = []
      for (let i = 0; i < POINT; i++) {
        circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10) / 40, num(10, -10) / 40))
      }
      draw()
    }

    //每帧绘制
    function draw() {
      context.clearRect(0, 0, canvas.width, canvas.height)
      for (let i = 0; i < POINT; i++) {
        drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r)
      }
      for (let i = 0; i < POINT; i++) {
        for (let j = 0; j < POINT; j++) {
          if (i + j < POINT) {
            let A = Math.abs(circleArr[i + j].x - circleArr[i].x),
              B = Math.abs(circleArr[i + j].y - circleArr[i].y)
            let lineLength = Math.sqrt(A * A + B * B)
            let C = 1 / lineLength * 7 - 0.009
            let lineOpacity = C > 0.03 ? 0.03 : C
            if (lineOpacity > 0) {
              drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i + j].x, circleArr[i + j].y, lineOpacity)
            }
          }
        }
      }
    }

    init()
    setInterval(function () {
      for (let i = 0; i < POINT; i++) {
        let cir = circleArr[i]
        cir.x += cir.moveX
        cir.y += cir.moveY
        if (cir.x > WIDTH) cir.x = 0
        else if (cir.x < 0) cir.x = WIDTH
        if (cir.y > HEIGHT) cir.y = 0
        else if (cir.y < 0) cir.y = HEIGHT

      }
      draw()
    }, 16)
  }

}